dipper@utastro.UUCP (Debbie Byrd) (08/20/85)
Today is the 100th anniversary of the first object known to be a SUPERnova. More on S Andromedae -- after this. August 20: A Supernova in Andromeda A supernova is a star that explodes. Supernovae are thought to occur every few decades in our galaxy -- but nobody has seen one in this galaxy for more than 400 years. So astronomers who study supernovae must turn their instruments to other galaxies. History's most famous extragalactic supernova was sighted in the Andromeda galaxy -- one hundred years ago today. The Andromeda galaxy is two million light-years away -- close enough to be seen with the naked eye as a patch of haze in a dark autumn night sky. When the supernova known as S Andromedae erupted in 1885, it looked like a new star that suddenly burst to life close to the center of the galaxy. In 1885, the prevailing theory on galaxies was that ours was the only one. Scientists at the time believed that S Andromedae lay only a few THOUSAND light-years from Earth and that it was one of the ordinary novae that erupt less violently -- and more frequently -- than supernovae. It wasn't until the 1920's that the cloud patch called Andromeda became known as a separate island of stars, one among billions of galaxies in the universe. Since Andromeda was now known to be MILLIONS of light-years away, astronomers realized that S Andromedae couldn't have appeared so bright from Earth and still be an ordinary nova. It was then that they coined the new name, supernova. Nowadays both amateur and professional astronomers use their telescopes to search for supernovae in other galaxies. and they find about two dozen supernovae every year! Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin